Add test for #3030

Author: hazzik

src/NHibernate.Test/NHSpecificTest/GH3030/ByCodeFixture.cs

@@ -0,0 +1,73 @@
+using System;
+using System.Linq;
+using NHibernate.Cfg.MappingSchema;
+using NHibernate.Mapping.ByCode;
+using NUnit.Framework;
+
+namespace NHibernate.Test.NHSpecificTest.GH3030
+{
+	[TestFixture]
+	public class ByCodeFixture : TestCaseMappingByCode
+	{
+		protected override HbmMapping GetMappings()
+		{
+			var mapper = new ModelMapper();
+			mapper.Class<Entity>(rc =>
+			{
+				rc.Table("Entity");
+				rc.Id(x => x.Id, m => m.Generator(Generators.Assigned));
+			});
+
+			return mapper.CompileMappingForAllExplicitlyAddedEntities();
+		}
+
+		protected override void OnSetUp()
+		{
+		}
+
+		protected override void OnTearDown()
+		{
+			using var session = OpenSession();
+			using var transaction = session.BeginTransaction();
+
+			session.CreateQuery("delete from System.Object").ExecuteUpdate();
+			transaction.Commit();
+		}
+
+		[Test]
+		public void LinqLeaksMemory()
+		{
+			WeakReference sessionReference = null;
+			WeakReference firstReference = null;
+			WeakReference secondReference = null;
+
+			new System.Action(
+				() =>
+				{
+					using var session = ((DebugSessionFactory) Sfi).ActualFactory.OpenSession();
+
+					var first = new Entity { Id = 1 };
+					var second = new Entity { Id = 2 };
+
+					_ = session.Query<Entity>().FirstOrDefault(f => f == first);
+					_ = session.Query<Entity>().FirstOrDefault(f => f == second);
+
+					sessionReference = new WeakReference(session, true);
+					firstReference = new WeakReference(first, true);
+					secondReference = new WeakReference(second, true);
+				})();
+
+			GC.Collect();
+			GC.WaitForPendingFinalizers();
+
+			Assert.That(sessionReference.Target, Is.Null);
+			Assert.That(firstReference.Target, Is.Null);
+			Assert.That(secondReference.Target, Is.Null);
+		}
+		
+		public class Entity 
+		{
+			public virtual int Id { get; set; }
+		}
+	}
+}